Stator for electric rotating machine and method of manufacturing the same

ABSTRACT

Disclosed is a method of manufacturing a stator for an electric rotating machine. The method includes the steps of: (1) forming a plurality of planar electric wires, each of the planar electric wires including a plurality of in-slot portions to be received in slots of a stator core and a plurality of turn portions to be located outside of the slots to connect the in-slot portions; (2) rolling each of the planar electric wires through plastic deformation into a spiral or circular-arc shape; (3) forming a hollow cylindrical stator coil by assembling the rolled electric wires through operations of making relative axial movement therebetween; and (4) assembling the stator core and the stator coil together to form the stator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority from Japanese PatentApplications No. 2009-244442 filed on Oct. 23, 2009 and No. 2010-232795filed on Oct. 15, 2010, the contents of which are hereby incorporated byreference in their entireties into this application.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to stators for electric rotating machinesthat are used in, for example, motor vehicles as electric motors andelectric generators, and to methods of manufacturing the stators.

2. Description of the Related Art

Conventionally, there are known stators for electric rotating machineswhich include a hollow cylindrical stator core and a stator coil.

The stator core has a plurality of slots that are formed in the radiallyinner surface of the stator core and spaced in the circumferentialdirection of the stator core. The stator coil is comprised of aplurality of electric wires mounted on the stator core. Each of theelectric wires includes a plurality of in-slot portions, which arereceived in the slots of the stator core, and a plurality of turnportions that are located outside of the slots to connect the in-slotportions.

Moreover, there is disclosed, for example in Japanese Patent ApplicationPublication No. 2001-145286, a method of manufacturing a stator.According to the method, to improve the space factors of the electricwires in the slots of the stator core, each of the electric wiresforming U-phase, V-phase, and W-phase windings of the stator coil isconfigured to have a rectangular cross section and have such an overallshape that when developed on a plane, the electric wire meanders in theform of cranks. Further, the stator coil is formed by: (1) stacking aplurality of belt-shaped electric wires, which make up the U-phase,V-phase, and W-phase windings, to form a planar electric wire assembly;and (2) rolling the planar electric wire assembly by a predeterminednumber of turns into a hollow cylindrical shape.

For the thus-formed stator coil, it is necessary for those in-slotportions of the electric wires which are to be received in the same slotof the stator core to be aligned in a radial direction of the statorcoil. However, due to springback of the electric wires which are onlyelastically deformed during the rolling step, it may be easy formisalignment between the corresponding in-slot portions of the electricwires to occur, rendering it difficult to keep the hollow cylindricalshape of the stator coil. Consequently, it may be difficult to easilyand accurately assemble the stator coil with the stator core.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided amethod of manufacturing a stator for an electric rotating machine. Thestator includes a hollow cylindrical stator core having a plurality ofslots that are formed in the radially inner surface of the stator coreand spaced in the circumferential direction of the stator core. Themethod comprising the steps of: (1) forming a plurality of planarelectric wires, each of the planar electric wires including a pluralityof in-slot portions to be received in the slots of the stator core and aplurality of turn portions to be located outside of the slots to connectthe in-slot portions; (2) rolling each of the planar electric wiresthrough plastic deformation into a spiral or circular-arc shape; (3)forming a hollow cylindrical stator coil by assembling the rolledelectric wires through operations of making relative axial movementtherebetween; and (4) assembling the stator core and the stator coiltogether to form the stator.

With the above method, since each of the planar electric wires is rolledthrough plastic deformation into the spiral or circular-arc shape, nospring back of the electric wires will occur after the rolling step.Consequently, in the subsequent step of forming the stator coil, it ispossible to easily and accurately perform the operations of makingrelative axial movement between the rolled electric wires, therebyfacilitating the assembling of the rolled electric wires. Further, afterthe step of forming the stator coil, it is possible to reliably preventmisalignment between the corresponding in-slot portions of the rolledelectric wires from occurring, thereby reliably keeping the hollowcylindrical shape of the stator coil. Consequently, in the subsequentstep of assembling, it is possible to easily and accurately assemble thestator core and the stator coil together. As a result, it is possible toimprove the productivity of the stator while ensuring both highdimensional accuracy and high reliability of the stator 20.

In addition, compared to the method disclosed in Japanese PatentApplication Publication No. 2001-145286, it is possible to shorten thelength of each of the electric wires. Consequently, the electric wirescan be formed using a smaller-scale machine and be more easily handledduring the manufacture of the stator. As a result, it is possible toachieve a higher productivity and a lower cost of the stator.

Preferably, in the step of forming the planar electric wires, each ofthe planar electric wires is formed to include a plurality of firstbulges. Each of the first bulges may be formed, on a surface of one ofthe in-slot portions of the planar electric wire or a surface of aportion of the planar electric wire which falls on an imaginary lineextending straight from the in-slot portion, so as to protrude from thein-slot portion in a radial direction of the stator core.

Further, in an embodiment of the invention, in the step of forming theplanar electric wires, each of the planar electric wires is formed sothat each of the turn portions of the planar electric wire includes apair of shoulder parts. Each of the shoulder parts adjoins one of thein-slot portions of the planar electric wire and is bent at asubstantially right angle to the in-slot portion to form a bend betweenthe shoulder part and the in-slot portion. Each of the first bulges ispreferably formed on a surface of one of the bends formed between theshoulder parts of the turn portions and the in-slot portions of theplanar electric wire.

Preferably, in the step of forming the planar electric wires, each ofthe planar electric wires is formed so that each of the turn portions ofthe electric wires is stepped to include a plurality of shoulder partsthat extend substantially perpendicular to the in-slot portions. Each ofthe planar electric wires is also formed to include a plurality ofsecond bulges. Each of the second bulges is formed on a surface of oneof bends formed between the shoulder parts of the turn portions of theplanar electric wire so as to protrude in a radial direction of thestator core.

In the step of forming the stator coil, each of the operations of makingrelative axial movement may be performed by axially moving a firstmember toward a second member; each of the first and second members maybe one of the rolled electric wires or an electric wire assemblycomprised of a plurality of the rolled electric wires.

Further, it is preferable that each of the operations be performed withat least one of the first and second members elastically deformed in aradial direction thereof.

According to another aspect of the present invention, there is provideda stator for an electric rotating machine, which is manufactured by themethod according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given hereinafter and from the accompanying drawings ofpreferred embodiments of the invention, which, however, should not betaken to limit the invention to the specific embodiments but are for thepurpose of explanation and understanding only.

In the accompanying drawings:

FIG. 1 is a perspective view of a stator for an electric rotatingmachine according to an embodiment of the invention;

FIG. 2 is a top view of the stator;

FIG. 3 is a side view of the stator;

FIG. 4 is a top view of a stator core of the stator;

FIG. 5 is a top view of one of stator core segments which together makeup the stator core;

FIG. 6 is a perspective view of a stator coil of the stator;

FIG. 7 is a side view of the stator coil;

FIG. 8 is a top view of the stator coil;

FIG. 9 is a bottom view of the stator coil;

FIG. 10A is a cross-sectional view illustrating the configuration ofelectric wires forming the stator coil;

FIG. 10B is a cross-sectional view illustrating a modification of theconfiguration of the electric wires shown in FIG. 10A;

FIG. 11A is a top view of one of the electric wires;

FIG. 11B is a front view of the one of the electric wires;

FIG. 12A is a perspective view illustrating a turn portion of one of theelectric wires;

FIG. 12B is a perspective view illustrating a plurality of turn portionsof the electric wires which are adjacent to one another;

FIG. 13 is a circuit diagram of the stator coil;

FIG. 14 is a schematic view illustrating the location of theradially-outermost in-slot portion of each of the electric wires in thestator core;

FIG. 15 is a schematic view illustrating the manner of extension of theelectric wire labeled (U1-4′) when viewed along the longitudinal axis Oof the stator core;

FIG. 16 is a tabular representation showing both the label of theelectric wire located at the radially outermost layer and the label ofthe electric wire located at the radially innermost layer in each of theslots of the stator core;

FIG. 17 is a schematic view illustrating the connection between those ofthe electric wires which together form a V-phase winding of the statorcoil when viewed from the radially inner side of the stator core;

FIG. 18 is a flow chart illustrating a method, according to theembodiment, of manufacturing the stator;

FIG. 19 is a perspective view illustrating an electric wire forming stepof the method;

FIGS. 20A and 20B are schematic views respectively illustrating anelectric wire material for forming one of the electric wires before andafter being bent in the electric wire forming step;

FIG. 21 is an axial end view of one of the electric wires which has beenrolled into a spiral shape in an electric wire rolling step of themethod;

FIG. 22A is a schematic view illustrating the operation of axiallymoving one of the rolled electric wires toward another one of the samein a stator coil forming step of the method;

FIG. 22B is a schematic view illustrating the operation of axiallymoving one of the rolled electric wires toward an electric wireassembly, which is comprised of plural of the rolled electric wires, inthe stator coil forming step;

FIG. 23A is a perspective view illustrating the relative axial movementbetween a pair of the rolled electric wires in the stator coil formingstep;

FIG. 23B is a cross-sectional view taken along the line A-A in FIG. 23A;

FIG. 23C is an axial end view of part of one of the rolled electricwires, wherein bulges 57 and 58 are enlarged for clarity;

FIG. 24A is a front view of an electric wire for forming the stator coilaccording to a first modification of the invention;

FIG. 24B is a front view of an electric wire for forming the stator coilaccording to a second modification of the invention;

FIG. 25A is a front view of an electric wire for forming the stator coilaccording to a third modification of the invention;

FIG. 25B is a front view of an electric wire for forming the stator coilaccording to a fourth modification of the invention;

FIG. 26 is a perspective view illustrating a turn portion of an electricwire for forming the stator coil according to a fifth modification ofthe invention;

FIG. 27A is a top view of an electric wire for forming the stator coilaccording to a sixth modification of the invention;

FIG. 27B is a front view of the electric wire according to the sixthmodification;

FIG. 28A is a perspective view illustrating a modification of a firstfixed jig which is used in the electric wire forming step;

FIG. 28B is a view along the K direction in FIG. 28A; and

FIG. 29A is a perspective view illustrating the process of formingbulges in an electric wire material according to a modification of theinvention; and

FIG. 29B is a perspective view illustrating the bulges formed in theelectric wire material by the process.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1-3 together show the overall configuration of a stator 20according to an embodiment of the invention.

The stator 20 is designed for use in, for example, an electric rotatingmachine which is configured to function both as an electric motor and asan electric generator in a motor vehicle. The electric rotating machinefurther includes a rotor (not shown) that is rotatably disposed so as tobe surrounded by the stator 20. The rotor includes a plurality ofpermanent magnets that form a plurality of magnetic poles on a radiallyouter periphery of the rotor to face a radially inner periphery of thestator. The polarities of the magnetic poles alternate between north andsouth in the circumferential direction of the rotor. In addition, in thepresent embodiment, the number of the magnetic poles formed in the rotoris equal to eight (i.e., four north poles and four south poles).

As shown in FIGS. 1-3, the stator 20 includes a hollow cylindricalstator core 30 and a three-phase stator coil 40 that is comprised of aplurality of (e.g., 48 in the present embodiment) electric wires 50mounted on the stator core 30. In addition, the stator 20 may furtherinclude insulating paper interposed between the stator core 30 and thestator coil 40.

The stator core 30 has, as shown in FIG. 4, a plurality of slots 31 thatare formed in the radially inner surface of the stator core 30 andspaced in the circumferential direction of the stator core 30 at apredetermined pitch. For each of the slots 31, the depth-wise directionof the slot 31 is coincident with a radial direction of the stator core30. In the present embodiment, there are provided two slots 31 permagnetic pole of the rotor that has the eight magnetic poles and perphase of the three-phase stator coil 40. Accordingly, the total numberof the slots 31 provided in the stator core 30 is equal to 48 (i.e.,2×8×3).

Moreover, in the present embodiment, the stator core 30 is composed upof, for example, 24 stator core segments 32 as shown in FIG. 5. Thestator core segments 32 are joined together so as to adjoin one anotherin the circumferential direction of the stator core 30. Each of thestator core segments 32 defines therein one of the slots 31. Further,each circumferentially-adjoining pair of the stator core segments 32together defines a further one of the slots 31 therebetween. Each of thestator core segments 32 also has two tooth portions 33, which radiallyextend to form the one of the slots 31 therebetween, and a back coreportion 34 that is located radially outward of the tooth portions 33 toconnect them. In addition, on the radially outer surfaces of the statorcore segments 32, there is fitted a cylindrical outer rim 37 (see FIGS.1-3).

In the present embodiment, each of the stator core segments 32 is formedby laminating a plurality of magnetic steel sheets with a plurality ofinsulating films interposed therebetween. It should be noted that otherconventional metal sheets may also be used instead of the magnetic steelsheets.

FIGS. 6-9 together show the configuration of the stator coil 40, whichis formed with the electric wires 50 into a hollow cylindrical shape.

As shown in FIGS. 6-9, the stator coil 40 has, as a whole, a straightpart 41 to be received in the slots 31 of the stator core 30, and a pairof coil end parts 42 that are respectively formed on opposite axialsides of the straight part 41 and to be located outside of the slots 31.Moreover, on one axial side of the straight part 41, U-phase, V-phase,and W-phase output terminals and U-phase, V-phase, and W-phase neutralterminals of the stator coil 40 protrude from the annular axial end faceof the coil end part 42, and a plurality of crossover parts 70 of theelectric wires 50 cross over the axial end face from the radially innerside to the radially outer side of the axial end face to connectcorresponding pairs of the electric wires 50.

Each of the electric wires 50 for forming the stator coil 40 isconfigured with, as shown in FIG. 10A, an electric conductor 67 and aninsulating coat 68 that covers the outer surface of the electricconductor 67. In the present embodiment, the electric conductor 67 ismade of copper and has a substantially rectangular cross section. Theinsulating coat 68 is two-layer structured to include an inner layer 68a and an outer layer 68 b. The thickness of the insulating coat 68(i.e., the sum of thicknesses of the inner and outer layers 68 a and 68b) is set to be in the range of 100 to 200 μm.

With such a large thickness of the two-layer structured insulating coat68, it is possible to reliably insulate the electric wires 50 from oneanother without interposing insulating paper therebetween. However, itis also possible to interpose insulating paper between the electricwires 50 so as to further enhance the electrical insulationtherebetween.

Further, the outer layer 68 b is made of an insulating material such asnylon. The inner layer 68 a is made of a thermoplastic resin having ahigher glass transition temperature than the outer layer 68 b or aninsulating material having no glass transition temperature such as apolyamide-imide resin. Consequently, the outer layers 68 b of theelectric wires 50 will be solidified by the heat generated by operationof the electric rotating machine earlier than the inner layers 68 a. Asa result, the surface hardness of the outer layers 68 b will beincreased, thereby enhancing the electrical insulation between theelectric wires 50.

Furthermore, as shown in FIG. 10B, it is also possible for each of theelectric wires 50 to further include a fusible coat 69 to cover theouter surface of the insulating coat 68; the fusible coat 69 may bemade, for example, of epoxy resin. In this case, the fusible coats 69 ofthe electric wires 50 will be fused by the heat generated by operationof the electric rotating machine earlier than the insulating coats 68,thereby bonding together those portions of the electric wires 50 whichare received in the same ones of the slots 31 of the stator core 30. Asa result, those portions of the electric wires 50 will be integratedinto a rigid body, thereby enhancing the mechanical strength thereof. Inaddition, the outer layers 68 b of the insulating coats 68 of theelectric wires 50 may also be made of PPS (polyphenylene sulfide).

FIGS. 11A-11B together show the shape of each of the electric wires 50before the electric wires 50 are rolled into a spiral shape as to bedescribed later.

As shown in FIGS. 11A-11B, each of the electric wires 50 is planar andwave-shaped to include a plurality of in-slot portions 51 and aplurality of turn portions 52. The in-slot portions 51 are spaced in thelongitudinal direction Y of the electric wire 50 at predeterminedpitches and extend perpendicular to the longitudinal direction Y. Eachof the in-slot portions 51 is to be received in a corresponding one ofthe slots 31 of the stator core 30. Each of the turn portions 52 extendsto connect a corresponding adjacent pair of the in-slot portions 51 andis to be located outside of the slots 31 of the stator core 30.

Specifically, the plurality of in-slot portions 51 include, at least, afirst in-slot portion 51A, a second in-slot portion 51B, and a thirdin-slot portion 51C. The first, second and third in-slot portions 51A,51B, and 51C are to be respectively received in three different slots 31of the stator core 30; the three slots 31 are circumferentially spacedat a pitch of six slots 31. On the other hand, the plurality of turnportions 52 include, at least, a first turn portion 52A and a secondturn portion 52B. The first turn portion 52A connects the first andsecond in-slot portions 51A and 51B and is to be located on one axialside of the stator core 30 outside of the slots 31. The second turnportion 52B connects the second and third in-slot portions 51B and 51Cand is to be located on the other axial side of the stator core 30outside of the slots 31.

More specifically, in the present embodiment, as shown in FIGS. 11A-11B,the plurality of in-slot portions 51 include first to twelfth in-slotportions 51A-51L which are to be sequentially received in eight slots 31that are circumferentially spaced at a pitch of six slots 31. In otherwords, the number of the in-slot portions 51 in each of the electricwires 50 is equal to 12. On the other hand, the plurality of turnportions 52 include first to eleventh turn portions 52A-52K which eachconnect a corresponding adjacent pair of the in-slot portions 51A-51Land are to be alternately located on the opposite axial sides of thestator core 30 outside of the slots 31. In other words, the number ofthe turn portions 52 in each of the electric wires 50 is equal to 11.

Moreover, the predetermined pitches X between the in-slot portions51A-51L in the longitudinal direction Y of the electric wire 50gradually decrease in a direction from the first in-slot portion 51A tothe twelfth in-slot portion 51L. That is,X1>X2>X3>X4>X5>X6>X7>X8>X9>X10>X11. In addition, the predeterminedpitches X1-X11 are set based on the circumferential distances betweenthe eight slots 31 of the stator core 30 in which the in-slot portions51A-51L are to be received. Each of the electric wires 50 furtherincludes a pair of lead portions 53 a and 53 b that are respectivelyformed at opposite ends of the electric wire 50 for connecting theelectric wire 50 with other electric wires 50. The lead portion 53 a isconnected to the first in-slot portion 51A via a half-turn portion 52Mthat extends from the first in-slot portion 51A to return inward (i.e.,rightward in FIG. 11B) in the longitudinal direction Y of the electricwire 50. The length of the half-turn portion 52M is substantially halfthe length of the first turn portion 52A. Consequently, the lead portion53 a is offset inward (i.e., rightward in FIG. 11B) in the longitudinaldirection Y from the first in-slot portion 51A by the length of thehalf-turn portion 52M. On the other hand, the lead portion 53 b isconnected to the twelfth in-slot portion 51L via a half-turn portion 52Nthat extends from the twelfth in-slot portion 51L to return inward(i.e., leftward in FIG. 11B) in the longitudinal direction Y of theelectric wire 50. The length of the half-turn portion 52N issubstantially half the length of the eleventh turn portion 52K.Consequently, the lead portion 53 b is offset inward (i.e., leftward inFIG. 11B) in the longitudinal direction Y from the twelfth in-slotportion 51L by the length of the half-turn portion 52N. Further, thelead portion 53 b is formed to include therein one of the crossoverparts 70 described previously.

Furthermore, as shown in FIG. 11A, each of the turn portions 52includes, substantially at the center thereof, a crank-shaped part 54that is bent to offset the turn portion 52 in a direction perpendicularto both the longitudinal direction Y of the electric wire 50 and theextending direction of the in-slot portions 51. Consequently, with thecrank-shaped parts 54, the electric wire 50 is stepped to successivelyoffset the in-slot portions 51 in the direction perpendicular to boththe longitudinal direction Y and the extending direction of the in-slotportions 51. It should be noted that the term “crank-shaped” is usedhere only for the purpose of describing the overall shape of the parts54 and does not restrict the internal angles between adjacent sectionsof the parts 54 to 90°.

Referring now to FIGS. 12A-12B, after forming the stator coil 40 withthe electric wires 50 and assembling the stator core 30 to the statorcoil 40, each of the turn portions 52 (i.e., 52A-52K) of the electricwires 50 is offset by the crank-shaped part 54 formed therein in aradial direction of the stator core 30. In addition, though not shown inFIGS. 12A-12B, each of the crank-shaped parts 54 formed in the turnportions 52 of the electric wires 50 extends parallel to a correspondingaxial end face 30 a of the stator core 30.

Further, in the present embodiment, the amount of radial offset made byeach of the crank-shaped parts 54 is set to be equal to the radialthickness of the in-slot portions 51 of the electric wires 50. Here, theamount of radial offset made by each of the crank-shaped parts 54 isdefined as the difference in radial position between the opposite endsof the crank-shaped part 54. Accordingly, for each of the electric wires50, the difference in radial position between each adjacent pair of thein-slot portions 51, which are connected by a corresponding one of theturn portions 52, is equal to the radial thickness (i.e., thickness inthe radial direction of the stator core 30) of the in-slot portions 51.

Setting the amount of radial offset as above, it is possible to arrangeeach adjacent pair of the turn portions 52 of the electric wires 50 inintimate contact with each other, as shown in FIG. 12B. As a result, theradial thickness of the coil end parts 42 of the stator coil 40 can beminimized. In addition, it is also possible to make each adjacent pairof the turn portions 52 of the electric wires 50 extend in thecircumferential direction of the stator core 30 without interferencetherebetween.

Moreover, as shown in FIGS. 12A-12B, each of the turn portions 52 of theelectric wires 50 includes a pair of shoulder parts 55 whichrespectively adjoin the pair of the in-slot portions 51 connected by theturn portion 52 and both extend substantially perpendicular to the pairof the in-slot portions 51 (or substantially parallel to thecorresponding axial end face 30 a of the stator core 30). Consequently,with the shoulder parts 55, the protruding height of each of the turnportions 52 from the corresponding axial end face 30 a of the statorcore 30 can be reduced. As a result, the axial length of the coil endparts 42 of the stator coil 40 can be reduced. In addition, the coil endparts 42 of the stator coil 40 are each comprised of those of the turnportions 52 of the electric wires 50 which are located on the same axialside of the stator core 30.

In the present embodiment, each of the shoulder parts 55 is bent at asubstantially right angle to the adjoining in-slot portion 51, forming abend between the shoulder part 55 and the adjoining in-slot portion 71.Further, a pair of bulges 57 are respectively formed on the radial endfaces of the bend (see also FIGS. 23A-23C). The bulges 57 are locatedcloser to the inside than the outside of the bend, and fall on animaginary line that extends straight from the adjoining in-slot portion51. The bulges 57 also protrude from the adjoining in-slot portion 51radially inward and radially outward, respectively.

Furthermore, in the present embodiment, there is specified the followingdimensional relationship: d1≦d2, where d1 is the length of each of theshoulder parts 55 of the electric wires 50 in the circumferentialdirection of the stator core 30 and d2 is the distance between eachcircumferentially-adjacent pair of the slots 31 of the stator core 30.

Specifying the above relationship, it is possible to preventinterference between each pair of the turn portions 52 of the electricwires 50 which respectively protrude from one circumferentially-adjacentpair of the slots 31 of the stator core 30. Consequently, it is possibleto prevent both the axial length and radial thickness of the coil endparts 42 of the stator coil 40 from being increased for preventing theabove-described interference.

Moreover, as shown in FIGS. 12A-12B, each of the turn portions 52 of theelectric wires 50 further includes two shoulder parts 56 between thecrank-shaped part 54 and each of the shoulder parts 55. Accordingly,each of the turn portions 52 of the electric wires 50 includes onecrank-shaped part 54, two shoulder parts 55, and four shoulder parts 56.Each of the shoulder parts 56 extends, like the shoulder parts 55,substantially perpendicular to the in-slot portions 51 (or substantiallyparallel to the corresponding axial end face 30 a of the stator core30). Consequently, with the shoulder parts 56, the protruding height ofeach of the turn portions 52 from the corresponding axial end face 30 aof the stator core 30 can be further reduced. As a result, the axiallength of the coil end parts 42 of the stator coil 40 can be furtherreduced. In addition, each of the turn portions 52 of the electric wires50 can be seen as being stepped on both sides of the crank-shaped part54 to reduce its protruding height from the corresponding axial end face30 a of the stator core 30.

Further, for each of bends formed between the shoulder parts 55 and 56,there are formed a pair of bulges 58 respectively on the radial endfaces of the bend. The bulges 58 are located closer to the inside thanthe outside of the bend, and protrude from the closet one of the in-slotportions 51 radially inward and radially outward, respectively.

In the present embodiment, the stator coil 40 is formed with the 48electric wires 50 as shown in FIGS. 11A-11B. It should be noted that thecrossover parts 70 may be omitted from some of the electric wires 50 forfacilitating the formation of the U-phase, V-phase, and W-phase outputterminals and the U-phase, V-phase, and W-phase neutral terminals in thestator coil 40. However, in any case, it is preferable that all of theelectric wires 50 have the same shape at least between the lead portions53 a and 53 b.

As described previously, each of the turn portions 52 of the electricwires 50 includes, substantially at the center thereof, the crank-shapedpart 54 by which the turn potion 52 is radially offset by the radialthickness of the in-slot portions 51. Accordingly, for each of theelectric wires 50, the difference in radial position between eachadjacent pair of the in-slot portions 51, which are connected by acorresponding one of the turn portions 52, is equal to the radialthickness of the in-slot portions 51. Moreover, for each of the electricwires 50, the first in-slot portion 51A is located most radially outwardwhile the twelfth in-slot portion 51L is located most radially inward;the predetermined pitches X between the in-slot portions 51A-51Lgradually decrease in a direction from the first in-slot portion 51A tothe twelfth in-slot portion 51L (see FIG. 11B). Consequently, those ofthe in-slot portions 51 of the electric wires 50 which are stacked in aradial direction of the stator coil 40 (or a radial direction of thestator core 30) can be aligned straight in the radial direction, therebyallowing the stator coil 40 to have a substantially perfecthollow-cylindrical shape as shown in FIGS. 6 and 7.

Furthermore, all of the ith in-slot portions 51 of the 48 electric wires50 are located respectively in the 48 slots 31 of the stator core 30 atthe same radial position, where i=1, 2, . . . , 12. For example, all ofthe first in-slot portions 51A of the 48 electric wires 50 are locatedrespectively in the 48 slots 31 and positioned most radially outward inthe respective slots 31; all of the twelfth in-slot portions 51L of the48 electric wires 50 are located respectively in the 48 slots 31 andpositioned most radially inward in the respective slots 31. With theabove location of the in-slot portions 51 of the electric wires 50, boththe outside and inside diameters of the stator coil 40 can be madeuniform in the circumferential direction of the stator core 30.

In the present embodiment, as shown in FIG. 13, the stator coil 40 isformed as a three-phase coil which is comprised of three phase windings(i.e., U-phase, V-phase, and W-phase windings) 43. Each of the U-phase,V-phase, and W-phase windings 43 is formed by serially connecting 16electric wires 50. Further, the U-phase output and neutral terminals arerespectively formed at the opposite ends of the U-phase winding 43; theV-phase output and neutral terminals are respectively formed at theopposite ends of the V-phase winding 43; and the W-phase output andneutral terminals are respectively formed at the opposite ends of theW-phase winding 43. Furthermore, the U-phase, V-phase, and W-phasewindings 43 are Y-connected to define a neutral point therebetween. Thatis, the U-phase, V-phase, and W-phase neutral terminals of the U-phase,V-phase, and W-phase windings 43 are joined together at the neutralpoint. Consequently, three-phase AC power is input to or output from thestator coil 40 via the U-phase, V-phase, and W-phase output terminals.

In FIGS. 14 and 15, the intersections between 12 dashed-line circles and48 radially-extending dashed lines represent the positions of thein-slot portions 51 of the electric wires 50. In addition, among thepositions of the in-slot portions 51, only the radially outermost andradially innermost ones are denoted by rectangles.

It can be seen from FIGS. 14 and 15 that in the present embodiment, ineach of the slots 31 of the stator core 30, the in-slot portions 51 ofthe electric wires 50 are radially stacked in 12 layers.

Further, in FIGS. 14 and 15, the numbers 1-48 of the slots 31 of thestator core 30 are respectively shown radially outside of the 48radially-extending dashed lines. In addition, in FIG. 14, each of the 48electric wires 50 is labeled radially outside of the slot 31 in whichthe first in-slot portion 51A of the electric wire 50 is located mostradially outward (i.e., located at the twelfth layer in the slot 31);each of the 48 electric wires 50 is also labeled radially inside of theslot 31 in which the twelfth in-slot portion 51L of the electric wire 50is located most radially inward (i.e., located at the first layer in theslot 31).

In the present embodiment, each of the U-phase, V-phase, and W-phasewindings 43 of the stator coil 40 is formed with first and secondelectric wire groups each consisting of eight electric wires 50. Thein-slot portions 51 of the electric wires 50 of the first group arereceived in eight common slots 31 of the stator core 30. Similarly, thein-slot portions 51 of the electric wires 50 of the second group arealso received in another eight common slots 31 of the stator core 30.That is, the in-slot portions 51 of the electric wires 50 of the firstgroup are received in different slots 31 from the in-slot portions 51 ofthe electric wires 50 of the second group.

For example, the U-phase winding 43 is formed with a first electric wiregroup, which consists of the electric wires 50 labeled (U1-1) to (U1-4)and (U1-1′) to (U1-4′), and a second electric wire group that consistsof the electric wires 50 labeled (U2-1) to (U2-4) and (U2-1′) to(U2-4′). The in-slot portions 51 of the (U1-1) to (U1-4) and (U1-1′) to(U 1-4′) electric wires 50 are received in the Nos. 1, 7, 13, 19, 25,31, 37, and 43 slots 31 of the stator core 30. On the other hand, thein-slot portions 51 of the (U2-1) to (U2-4) and (U2-1′) to (U2-4′)electric wires 50 are received in the Nos. 2, 8, 14, 20, 26, 32, 38, and44 slots 31 of the stator core 30.

FIG. 14 illustrates, from one axial side of the stator core 30, thearrangement of each of the 48 electric wires 50 by taking the (U1-1)electric wire 50 as an example. Specifically, in FIG. 14, the positionsof the in-slot portions 51 of the (U1-1) electric wire 50 are denoted byblack rectangles; those of the turn portions 52 of the (U1-1) electricwire 50 which are located on the one axial side of the stator core 30(i.e., on the front side of the paper surface of FIG. 14) are denoted bycircumferentially-extending heavy lines; and those of the turn portions52 of the (U1-1) electric wire 50 which are located on the other axialside of the stator core 30 (i.e., on the rear side of the paper surfaceof FIG. 14) are denoted by circumferentially-extending two-dot dashedlines. As seen from FIG. 14, for the (U1-1) electric wire 50, the firstin-slot portion 51A is located at the twelfth layer (i.e., the radiallyoutermost layer) in the No. 1 slot 31; the twelfth in-slot portion 51Lis located at the first layer (i.e., the radially innermost layer) inthe No. 19 slot 31; the first to the twelfth in-slot portions 51A-51Lare circumferentially spaced at a six-slot pitch; and the radialpositions of the in-slot portions 51A-51L are successively offsetradially inward by one layer each time.

FIG. 15 illustrates, from the other axial side of the stator core 30,the arrangement of each of the 48 electric wires 50 by taking the(U1-4′) electric wire 50 as an example. Specifically, in FIG. 15, thepositions of the in-slot portions 51 of the (U1-4′) electric wire 50 aredenoted by black rectangles; those of the turn portions 52 of the(U1-4′) electric wire 50 which are located on the other axial side ofthe stator core 30 (i.e., on the front side of the paper surface of FIG.15) are denoted by circumferentially-extending heavy lines; and those ofthe turn portions 52 of the (U1-4′) electric wire 50 which are locatedon the one axial side of the stator core 30 (i.e., on the rear side ofthe paper surface of FIG. 15) are denoted by circumferentially-extendingtwo-dot dashed lines. As seen from FIG. 15, for the (U1-4′) electricwire 50, the first in-slot portion 51A is located at the twelfth layerin the No. 43 slot 31; the twelfth in-slot portion 51L is located at thefirst layer in the No. 13 slot 31; the first to the twelfth in-slotportions 51A-51L are circumferentially spaced at a six-slot pitch; andthe radial positions of the in-slot portions 51A-51L are successivelyoffset by one layer each time.

As described previously, in the present embodiment, the stator core 30has the 48 slots 31 formed therein, while the stator coil 40 is formedwith the 48 electric wires 50. The electric wires 50 are mounted on thestator core 30 so that they are offset from one another in thecircumferential direction of the stator core 30 by one slot pitch of thestator core 30. Consequently, the first in-slot portions 51A of the 48electric wires 50 are respectively located at the radially outermostlayers (i.e., the twelfth layers) in the 48 slots 31; the twelfthin-slot portions 51L of the 48 electric wires 50 are respectivelylocated at the radially innermost layers (i.e., the first layers) in the48 slots 31.

FIG. 16 shows both the label of the electric wire 50 located at theradially outermost layer and the label of the electric wire 50 locatedat the radially innermost layer in each of the slots 31 of the statorcore 30.

In the present embodiment, for each of the 48 electric wires 50 formingthe stator coil 40, the radial distances from the axis O of the statorcore 30 to the in-slot portions 51 of the electric wire 50 successivelydecrease in the sequence from the first in-slot portion 51A to thetwelfth in-slot portion 51L. Moreover, for each of the 48 electric wires50, the difference in radial distance from the axis O of the stator core30 between each adjacent pair of the in-slot portions 51, which areconnected by a corresponding one of the turn portions 52, is equal tothe radial thickness of the in-slot portions 51.

For example, referring back to FIG. 15, for the (U1-4′) electric wire50, there is satisfied the following relationship: r43>r1>r7>r13. Here,r43 represents the radial distance from the axis O of the stator core 30to the first in-slot portion 51A that is located at the twelfth layer inthe No. 43 slot 31; r1 represents the radial distance from the axis O tothe second in-slot portion 51B that is located at the eleventh layer inthe No. 1 slot 31; r7 represents the radial distance from the axis O tothe third in-slot portion 51C that is located at the tenth layer in theNo. 7 slot 31; and r13 represents the radial distance from the axis O tothe fourth in-slot portion 51D that is located at the ninth layer in theNo. 13 slot 31. Further, the radial distances r43, r1, r7, and r13successively decrease in decrements of the radial thickness of thein-slot portions 51.

Next, with reference to FIGS. 13 and 16-17, the manner of seriallyconnecting the 16 electric wires 50 for forming the V-phase winding 43of the stator coil 40 will be described. In addition, it should be notedthat the electric wires 50 for forming the U-phase and W-phase windings43 of the stator coil 40 are also connected in the same manner as thosefor forming the V-phase winding 43. As shown in FIG. 13, the V-phasewinding 43 is formed by serially connecting the (V1-1) to (V1-4),(V1-1′) to (V1-V4′), (V2-1) to (V2-4), and (V2-1′) to (V2-4′) electricwires 50.

Specifically, to the V-phase output terminal, there is connected thefirst in-slot portion 51A-side end of the (V1-1) electric wire 50.Moreover, as shown in FIGS. 16 and 17, for the (V1-1) electric wire 50,the first in-slot portion 51A is located at the radially outermost layer(i.e., the twelfth layer) in the No. 5 slot 31 of the stator core 30,while the twelfth in-slot portion 51L is located at the radiallyinnermost layer (i.e., the first layer) in the No. 23 slot 31.

To the twelfth in-slot portion 51L-side end of the (V1-1) electric wire50, there is connected the first in-slot portion 51A-side end of the(V1-2) electric wire 50. Moreover, for the (V1-2) electric wire 50, thefirst in-slot portion 51A is located at the radially outermost layer inthe No. 17 slot 31, while the twelfth in-slot portion 51L is located atthe radially innermost layer in the No. 35 slot 31.

To the twelfth in-slot portion 51L-side end of the (V1-2) electric wire50, there is connected the first in-slot portion 51A-side end of the(V1-3) electric wire 50. Moreover, for the (V1-3) electric wire 50, thefirst in-slot portion 51A is located at the radially outermost layer inthe No. 29 slot 31, while the twelfth in-slot portion 51L is located atthe radially innermost layer in the No. 47 slot 31.

To the twelfth in-slot portion 51L-side end of the (V1-3) electric wire50, there is connected the first in-slot portion 51A-side end of the(V1-4) electric wire 50. Moreover, for the (V1-4) electric wire 50, thefirst in-slot portion 51A is located at the radially outermost layer inthe No. 41 slot 31, while the twelfth in-slot portion 51L is located atthe radially innermost layer in the No. 11 slot 31.

To the twelfth in-slot portion 51L-side end of the (V1-4) electric wire50, there is connected the first in-slot portion 51A-side end of the(V2-1) electric wire 50. Moreover, for the (V2-1) electric wire 50, thefirst in-slot portion 51A is located at the radially outermost layer inthe No. 6 slot 31, while the twelfth in-slot portion 51L is located atthe radially innermost layer in the No. 24 slot 31.

To the twelfth in-slot portion 51L-side end of the (V2-1) electric wire50, there is connected the first in-slot portion 51A-side end of the(V2-2) electric wire 50. Moreover, for the (V2-2) electric wire 50, thefirst in-slot portion 51A is located at the radially outermost layer inthe No. 18 slot 31, while the twelfth in-slot portion 51L is located atthe radially innermost layer in the No. 36 slot 31.

To the twelfth in-slot portion 51L-side end of the (V2-2) electric wire50, there is connected the first in-slot portion 51A-side end of the(V2-3) electric wire 50. Moreover, for the (V2-3) electric wire 50, thefirst in-slot portion 51A is located at the radially outermost layer inthe No. 30 slot 31, while the twelfth in-slot portion 51L is located atthe radially innermost layer in the No. 48 slot 31.

To the twelfth in-slot portion 51L-side end of the (V2-3) electric wire50, there is connected the first in-slot portion 51A-side end of the(V2-4) electric wire 50. Moreover, for the (V2-4) electric wire 50, thefirst in-slot portion 51A is located at the radially outermost layer inthe No. 42 slot 31, while the twelfth in-slot portion 51L is located atthe radially innermost layer in the No. 12 slot 31.

To the twelfth in-slot portion 51L-side end of the (V2-4) electric wire50, there is connected the twelfth in-slot portion 51L-side end of the(V2-4′) electric wire 50. Moreover, for the (V2-4′) electric wire 50,the first in-slot portion 51A is located at the radially outermost layerin the No. 48 slot 31, while the twelfth in-slot portion 51L is locatedat the radially innermost layer in the No. 18 slot 31.

To the first in-slot portion 51A-side end of the (V2-4′) electric wire50, there is connected the twelfth in-slot portion 51L-side end of the(V2-3′) electric wire 50. Moreover, for the (V2-3′) electric wire 50,the first in-slot portion 51A is located at the radially outermost layerin the No. 36 slot 31, while the twelfth in-slot portion 51L is locatedat the radially innermost layer in the No. 6 slot 31.

To the first in-slot portion 51A-side end of the (V2-3′) electric wire50, there is connected the twelfth in-slot portion 51L-side end of the(V2-2′) electric wire 50. Moreover, for the (V2-2′) electric wire 50,the first in-slot portion 51A is located at the radially outermost layerin the No. 24 slot 31, while the twelfth in-slot portion 51L is locatedat the radially innermost layer in the No. 42 slot 31.

To the first in-slot portion 51A-side end of the (V2-2′) electric wire50, there is connected the twelfth in-slot portion 51L-side end of the(V2-1′) electric wire 50. Moreover, for the (V2-1′) electric wire 50,the first in-slot portion 51A is located at the radially outermost layerin the No. 12 slot 31, while the twelfth in-slot portion 51L is locatedat the radially innermost layer in the No. 30 slot 31.

To the first in-slot portion 51A-side end of the (V2-1′) electric wire50, there is connected the twelfth in-slot portion 51L-side end of the(V1-4′) electric wire 50. Moreover, for the (V1-4′) electric wire 50,the first in-slot portion 51A is located at the radially outermost layerin the No. 47 slot 31, while the twelfth in-slot portion 51L is locatedat the radially innermost layer in the No. 17 slot 31.

To the first in-slot portion 51A-side end of the (V1-4′) electric wire50, there is connected the twelfth in-slot portion 51L-side end of the(V1-3′) electric wire 50. Moreover, for the (V1-3′) electric wire 50,the first in-slot portion 51A is located at the radially outermost layerin the No. 35 slot 31, while the twelfth in-slot portion 51L is locatedat the radially innermost layer in the No. 5 slot 31.

To the first in-slot portion 51A-side end of the (V1-3′) electric wire50, there is connected the twelfth in-slot portion 51L-side end of the(V1-2′) electric wire 50. Moreover, for the (V1-2′) electric wire 50,the first in-slot portion 51A is located at the radially outermost layerin the No. 23 slot 31, while the twelfth in-slot portion 51L is locatedat the radially innermost layer in the No. 41 slot 31.

To the first in-slot portion 51A-side end of the (V1-2′) electric wire50, there is connected the twelfth in-slot portion 51L-side end of the(V1-1′) electric wire 50. Moreover, for the (V1-1′) electric wire 50,the first in-slot portion 51A is located at the radially outermost layerin the No. 11 slot 31, while the twelfth in-slot portion 51L is locatedat the radially innermost layer in the No. 29 slot 31. In addition, thefirst in-slot portion 51A-side end of the (V1-1′) electric wire 50 isconnected to the V-phase neutral terminal of the stator coil 40.

Further, as described previously, each of the electric wires 50 has thelead portion 53 a formed at the first in-slot portion 51A-side endthereof and the lead portion 53 b formed at the twelfth in-slot portion51L-side end thereof (see FIGS. 11A-11B). The lead portion 53 a isconnected to the first in-slot portion 51A via the half-turn portion52M, and the lead portion 53 b is connected to the twelfth in-slotportion 51L via the half-turn portion 52N. The lead portion 53 b alsohas the crossover part 70 formed therein. In the present embodiment, theconnection between the electric wires 50 is made by weldingcorresponding pairs of the lead portions 53 a and 53 b of the electricwires 50.

For example, the (V1-1) electric wire 50 has the first in-slot portion51A located at the radially outermost layer in the No. 5 slot 31 of thestator core 30 and the twelfth in-slot portion 51L located at theradially innermost layer in the No. 23 slot 31. The lead portion 53 b ofthe (V1-1) electric wire 50 is offset, by the length of the half-turnportion 52N in the circumferential direction of the stator core 30, fromthe No. 23 slot 31 to the vicinity of the No. 20 slot 31. On the otherhand, the (V1-2) electric wire 50 has the first in-slot portion 51Alocated at the radially outermost layer in the No. 17 slot 31 and thetwelfth in-slot portion 51L located at the radially innermost layer inthe No. 35 slot 31. The lead portion 53 a of the (V1-2) electric wire 50is offset, by the length of the half-turn portion 52M in thecircumferential direction of the stator core 30, from the No. 17 slot 31to the vicinity of the No. 20 slot 31. Further, as shown in FIGS. 6-9,the lead portion 53 b of the (V1-1) electric wire 50 is bent radiallyoutward at a substantially right angle to extend from the radially innerperiphery of the stator coil 40 to the lead portion 53 a of the (V1-2)electric wire 50 which is located on the radially outer periphery of thestator coil 40; then, the lead portion 53 b of the (V1-1) electric wire50 is welded to the lead portion 53 a of the (V1-2) electric wire 50. Inother words, the twelfth in-slot portion 51L-side end of the (V1-1)electric wire 50 is joined to the first in-slot portion 51A-side end ofthe (V1-2) electric wire 50 by welding.

Moreover, in the present embodiment, all of the corresponding pairs ofthe lead portions 53 a and 53 b of the electric wires 50 are weldedradially outside of the radially outermost turn portions 52 of theelectric wires 50. To this end, each of the lead portions 53 b of theelectric wires 50 is configured to include the crossover part 70 thatcrosses over the annular axial end face of the stator coil 40 (morespecifically, the annular axial end face of the coil end part 42 of thestator coil 40 which is comprised of the turn portions 52 of theelectric wires 50) from the radially inside to the radially outside ofthe axial end face. Consequently, it is possible to reliably prevent thetwelfth in-slot portions 51L of the electric wires 50, which are locatedmost radially inward in the slots 31 of the stator core 30, fromprotruding radially inward. As a result, it is possible to reliablyprevent the stator coil 40 from interfering with the rotor of theelectric rotating machine which is located radially inside of the stator20.

Furthermore, in the present embodiment, as shown in FIG. 8, each of thecrossover parts 70 of the electric wires 50 is crank-shaped to include apair of radially-extending end sections 70 a and 70 b. With such ashape, it is possible to facilitate the bending of the lead portions 53b of the electric wires 50 for forming the crossover parts 70 and thewelding of the corresponding pairs of the lead portions 53 a and 53 b ofthe electric wires 50.

In addition, as shown in FIGS. 6 and 8, on the annular axial end face ofthe stator coil 40, the crossover parts 70 occupy substantially ¾ of thefull angular range of the axial end face; the full angular range is360°. Further, within the remaining ¼ of the full angular range, thereare sequentially arranged the V-phase neutral terminal, the W-phaseoutput terminal, the U-phase neutral terminal, the V-phase outputterminal, the W-phase neutral terminal, and the U-phase output terminalof the stator coil 40. That is, on the axial end face of the stator coil40, the U-phase, V-phase, and W-phase output terminals are arranged inthe same angular range as the U-phase, V-phase, and W-phase neutralterminals; the crossover parts 70 are arranged in a different angularrange from the U-phase, V-phase, and W-phase output terminals and theU-phase, V-phase, and W-phase neutral terminals.

The stator core 30 is assembled to the above-described stator coil 40 byinserting the tooth portions 33 of the stator core segments 32respectively into the spaces formed between the stacks of the in-slotportions 51 of the electric wires 50 from the radially outside of thestator coil 40. Consequently, each of the in-slot portions 51 of theelectric wires 50 forming the stator coil 40 is received in acorresponding one of the slots 31 of the stator core 30. Morespecifically, for each of the electric wires 50, each adjacent pair ofthe in-slot portions 51 are respectively received in a correspondingpair of the slots 31 of the stator core 30 which are circumferentiallyspaced at a six-slot pitch. Moreover, each of the turn portions 52,which connects a corresponding pair of the in-slot portions 51,protrudes from a corresponding one of the axial end faces of the statorcore 30.

After having described the configuration of the stator 20 according tothe present embodiment, a method of manufacturing the stator 20 will bedescribed hereinafter. Referring to FIG. 18, in the present embodiment,the method of manufacturing the stator 20 includes an electric wireforming step 101, an electric wire rolling step 102, a stator coilforming step 103, and a stator core mounting step 104.

First, in the electric wire forming step 101, the planar, wave-shapedelectric wires 50 as shown in FIGS. 11A-11B are formed by shaping aplurality of (e.g., 48 in the present embodiment) electric wirematerials 50 a.

Specifically, referring to FIGS. 19 and 20A-20B, each of the electricwire materials 50 a is shaped to form one of the electric wires 50 usinga pair of first and second fixed jigs 81 and 82 and a rotating jig 83.The first and second fixed jigs 81 and 82 are opposed to each other soas to hold the electric wire material 50 a therebetween. The rotatingjig 83 is rotatably mounted to a supporting shaft 83 a, so as to bendthe electric wire material 50 a held between the first and second fixedjigs 81 and 82 toward the first fixed jig 81. The first fixed jig 81 hasa substantially right-angled corner portion 81 a which makes contactwith, when the electric wire material 50 a is bent, the bent portion ofthe electric wire material 50 a. In addition, the corner portion 81 a isrounded with a constant radius of curvature R.

More specifically, in this step, as shown in FIG. 20A, a portion of theelectric wire material 50 a which makes up one of the in-slot portions51 of the electric wire 50 is first held between the first and secondfixed jigs 81 and 82. Then, as shown in FIG. 20B, the rotating jig 83 isrotated about the supporting axis 83 a toward the first fixed jig 81,thereby pressing the electric wire material 50 a against the cornerportion 81 a of the first fixed jig 81. Consequently, that portion ofthe electric wire material 50 a which adjoins the portion held betweenthe first and second fixed jigs 81 and 82 is bent along the surface ofthe corner portion 81 a at a substantially right angle to the portionheld between the jigs 81 and 82, thereby forming a shoulder part 55 ofthe electric wire 50. Further, during the bending, a pair of bulges 57,which are shown in FIGS. 23A-23C but omitted from FIG. 20B, arerespectively formed on the radial end faces (i.e., the surfaces parallelto the paper surface of FIG. 20B) of the bend. The bulges 57 are locatedcloser to the inside than the outside of the bend, and fall on animaginary line that extends straight from the portion of the electricwire material 50 a held between the first and second fixed jigs 81 and82. The bulges 57 also protrude from the portion of the electric wirematerial 50 a held between the first and second fixed jigs 81 and 82radially inward and radially outward, respectively. In addition, asshown in FIG. 20B, the width of the electric wire material 50 a isreduced at the bend from an initial value T to a smaller value t due tothe formation of the bulges 57.

Further, in this step, by repeatedly operating the jigs 81-83 in thesame manner as described above for that portion of the electric wirematerial 50 a which adjoins the just-formed shoulder part 55, a shoulderpart 56 is obtained with a bend formed between the shoulder parts 55 and56. Moreover, a pair of bulges 58 as shown in FIGS. 23A and 23C arerespectively formed on the radial end faces of the bend. The bulges 58are located closer to the inside than the outside of the bend, and alsoprotrude from that portion of the electric wire material 50 a whichmakes up the in-slot portion 51 of the electric wire 50.

Furthermore, in this step, by repeatedly operating the jigs 81-83 in thesame manner as described above for each of all the electric wirematerials 50 a, the plurality of (e.g., 48 in the present embodiment)electric wires 50 as shown in FIGS. 11A-11B are obtained.

In the electric wire rolling step 102, each of the planar electric wires50 formed in the electric wire forming step 101 is further rolled,through plastic deformation, by a predetermined number of turns into aspiral or circular-arc shape.

In the present embodiment, as shown in FIG. 21, each of the electricwires 50 is rolled by about one and a half turns into a spiral shape.Specifically, in this step, the electric wire 50 is first rolled aroundthe outer surface of a cylindrical core member (not shown), which has aplurality of predetermined outer diameters, by one turn; during therolling, the electric wire 50 is pressed against the outer surface ofthe cylindrical core member by a first pressing jig (not shown) that isdisposed radially outside of the electric wire 50, thereby beingplastically deformed. Then, a hollow cylindrical core member (notshown), which also has a plurality of predetermined outer diameters, isdisposed on the first pressing jig. Thereafter, the electric wire 50 isfurther rolled around the outer surface of the hollow cylindrical coreby about a half turn; during the rolling, the electric wire 50 ispressed against the outer surface of the hollow cylindrical core by asecond pressing jig (not shown) that is disposed on the radially outsideof the about half turn of the electric wire 50, thereby beingplastically deformed.

It should be noted that each of the electric wires 50 may also be rolledby less than one turn into a circular-arc shape as shown in FIG. 22A.

In the stator coil forming step 103, the rolled electric wires 50 areassembled together, through operations of making relative axial movementtherebetween, to form the stator coil 40.

Specifically, in this step, as shown in FIG. 22A, a pair of the electricwires 50 are assembled together by: (1) placing them so that they areoffset from each other in the circumferential direction (i.e., thehorizontal direction in FIG. 22A) by one slot pitch of the stator core30; and (2) axially (i.e., in the vertical direction in FIG. 22A) movingone of them (i.e., the upper one in FIG. 22A) toward the other (i.e.,the lower one in FIG. 22A).

Further, by repeating the above placing and moving operations, anelectric wire assembly 50 b are obtained which includes a plurality of(e.g., 4 in FIG. 22B) the electric wires 50. Furthermore, by repeatingthe above placing and moving operations, as shown in FIG. 22B, anelectric wire 50 is further assembled to the electric wire assembly 50b, thereby forming a larger electric wire assembly 50 b.

In the present embodiment, the stator coil 40 is formed by assemblingthe electric wires 50 one by one. More specifically, the stator coil 40is formed by each time assembling only one electric wire 50 to anotherelectric wire 50 in the same manner as illustrated in FIG. 22A or to anelectric wire assembly 50 b in the same manner as illustrated in FIG.22B.

It should be noted that the stator coil 40 can also be formed by firstforming a plurality of electric wire assemblies 50 b and then assemblingthe electric wire assemblies 50 b together.

In the present embodiment, in assembling the electric wires 50, theelectric wires 50 or the electric wire assemblies 50 b are elasticallydeformed in the radial direction, so as to minimize interference betweenthe electric wires 50 and the electric wire assemblies 50 b and therebyfacilitate relative axial movement therebetween.

For example, referring back to FIG. 21, when a load F is applied to boththe ends of an electric wire 50 in a direction to unroll the electricwire 50, the electric wire 50 will be expanded radially outward.Consequently, when another electric wire 50 is axially moved into thespace formed radially inside of the electric wire 50, interferencebetween the two electric wires 50 will be reduced, thereby facilitatingthe assembly of the two electric wires 50.

Similarly, though not graphically shown, when a load F is applied toeach of the ends of the electric wires 50 included in an electric wireassembly 50 b, the electric wires 50 will be expanded radially outward.Consequently, when an electric wire 50 is axially moved into the spaceformed radially inside of the electric wire assembly 50 b, interferencebetween the electric wire 50 and the electric wire assembly 50 b will bereduced, thereby facilitating the assembly of the electric wire 50 tothe electric wire assembly 50 b.

In the present embodiment, as described previously, each of the electricwires 50 has the bulges 57 formed on the radial end faces of the bendsformed between the in-slot portions 51 and the shoulder parts 55 of theturn portions 52. Consequently, referring to FIGS. 23A-23C, during therelative axial movement between any pair of the electric wires 50, onlythe bulges 57 of one of the pair of the electric wires 50 will makepoint contact with the corresponding in-slot portions 51 of the other.Further, after the electric wires 50 are assembled together, eachradially-adjacent pair of the in-slot portions 51 of the electric wires50 will be kept apart from each other in the radial direction by thebulges 57 of the electric wires 50.

Generally, the insulating coat 68 of each of the electric wires 50 haspinholes and voids formed therein; through the pinholes, air can comeinto contact with the electric conductor 67 of the electric wire 50.Further, the voids may become pinholes when the outer surface of theinsulating coat 68 is damaged by, for example, a frictional forceapplied thereto. Furthermore, when the pinholes of an adjacent pair ofthe electric wires 50 are located close to each other, an electricalshort circuit may occur upon the intrusion of an electrolytic solution(e.g., a saline) into those pinholes.

However, in the present embodiment, as described previously, during therelative axial movement between any pair of the electric wires 50, onlythe bulges 57 of one of the pair of the electric wires 50 will makepoint contact with the in-slot portions 51 of the other. Consequently,the frictional force applied to the in-slot portions 51 of the electricwires 50 will be considerably reduced in comparison with the case wherethere are no bulges formed in the electric wires 50 and thus the in-slotportions 51 of one of the pair of the electric wires 50 respectivelymake surface contact with those of the other. As a result, it ispossible to prevent the insulating coats 68 of the in-slot portions 51of the electric wires 50 from being damaged due to the frictional forceand thus to prevent the pinholes formed in the insulating coats 68 ofthe in-slot portions 51 from being located close to each other.Furthermore, as described previously, after the electric wires 50 areassembled together, each radially-adjacent pair of the in-slot portions51 of the electric wires 50 will be kept apart from each other in theradial direction by the bulges 57 of the electric wires 50.Consequently, the creepage distances between the pinholes formed in theinsulating coats 68 of the in-slot portions 51 of the electric wires 50will be increased. Therefore, according to the present embodiment, it ispossible to reliably prevent insulation failure between the in-slotportions 51 of the electric wires 50.

Furthermore, in the present embodiment, as described previously, each ofthe electric wires 50 also has the bulges 58 formed on the radial endfaces of the bends formed between the shoulder parts 55 and 56 of theturn portions 52, as shown in FIGS. 23A and 23C. Consequently, after theelectric wires 50 are assembled together, each radially-adjacent pair ofthe turn portions 52 of the electric wires 50 will be kept apart fromeach other in the radial direction by the bulges 58 of the turn portions52. As a result, the creepage distances between the pinholes formed inthe insulating coats 68 of the turn portions 52 of the electric wires 50will be increased. Therefore, according to the present embodiment, it isalso possible to reliably prevent insulation failure between the turnportions 52 of the electric wires 50.

Moreover, in the present embodiment, referring to FIG. 23B, there isspecified, through experimental investigation, the following dimensionalrelationship: 1<W/L≦1.1, where W is the radial thickness of the electricwires 50 at those portions where the bulges 57 or 58 are formed and L isthe radial thickness of the electric wires 50 at those portions where nobulges are formed.

Specifying the above relationship, it is possible to reliably preventthe insulating coats 68 of the electric wires 50 from being damaged dueto overstress, thereby reliably ensuring insulation between the electricwires 50. In addition, W and L may be respectively set to, for example,2.1 mm and 2.0 mm.

After assembling all of the electric wires 50 together as describedabove, the corresponding pairs of the lead portions 53 a and 53 b of theelectric wires 50 are joined together by, for example, welding. As aresult, the stator coil 40 as shown in FIGS. 6-9 is obtained.

In the subsequent stator core mounting step 104, the stator core 30 ismounted to the stator coil 40 formed in the stator coil forming step103.

Specifically, in this step, the tooth portions 33 of the stator coresegments 32 are respectively inserted into the spaces formed between thestacks of the in-slot portions 51 of the electric wires 50 from theradially outside of the stator coil 40. Then, the outer rim 37 is fittedonto the radially outer surfaces of the stator core segments 32. As aresult, the stator core 30 and the stator coil 40 are assembledtogether, forming the stator 20 as shown in FIGS. 1-3.

According to the present embodiment, it is possible to achieve thefollowing advantages.

In the present embodiment, the method of manufacturing the stator 20includes the electric wire forming step 101, the electric wire rollingstep 102, the stator coil forming step 103, and the stator core mountingstep 104. In the electric wire forming step 101, the planar, wave-shapedelectric wires 50 as shown in FIGS. 11A-11B are formed by shaping theelectric wire materials 50 a. Each of the electric wires 50 includes thein-slot portions 51 to be received in the slots 31 of the stator core 30and the turn portions 52 to be located outside of the slots 31 toconnect the in-slot portions 51. In the electric wire rolling step 102,each of the planar electric wires 50 is rolled, through plasticdeformation, by about one and a half turn into the spiral shape as shownin FIG. 21. In the stator coil forming step 103, the rolled electricwires 50 are assembled together, through operations of making relativeaxial movement therebetween, to form the stator coil 40 as shown inFIGS. 6-9. In the stator core mounting step 104, the stator core 30 ismounted to the stator coil 40 (in other words, the stator core 30 andthe stator coil 40 are assembled together), forming the stator 20 asshown in FIGS. 1-3.

With the above method, since each of the electric wires 50 is rolledthrough plastic deformation in the electric wire rolling step 102, nospring back of the electric wires 50 will occur after the step 102.Consequently, in the subsequent stator coil forming step 103, it ispossible to easily and accurately operate (i.e., place and axially move)the rolled electric wires 50, thereby facilitating the assembling of theelectric wires 50. Further, after the step 103, it is possible toreliably prevent misalignment between the corresponding in-slot portions50 of the electric wires 50 from occurring, thereby reliably keeping thehollow cylindrical shape of the stator coil 40. Consequently, in thestator core mounting step 104, it is possible to easily and accuratelymount the stator core 30 to the stator coil 40. As a result, it ispossible to improve the productivity of the stator 20 while ensuringboth high dimensional accuracy and high reliability of the stator 20.

In addition, compared to the method disclosed in Japanese PatentApplication Publication No. 2001-145286, it is possible to shorten thelength of each of the electric wires 50. Consequently, the electricwires 50 can be shaped using a smaller-scale shaping machine and be moreeasily handled during the manufacture of the stator 20. As a result, itis possible to achieve a higher productivity and a lower cost of thestator 20.

In the present embodiment, in the electric wire forming step 101, eachof the electric wires 50 is formed to include the bulges 57. Each of thebulges 57 is formed, on a radial end face of a portion of the electricwire 50 which falls on an imaginary line extending straight from one ofthe in-slot portions 51 of the electric wire 50, so as to protrude fromthe in-slot portion 51 radially inward or radially outward. Moreparticularly, in the present embodiment, each of the bulges 57 is formedon a radial end face of one of the bends formed between the shoulderparts 55 of the turn portions 52 and the in-slot portions 51 of theelectric wire 50.

Consequently, during the relative axial movement between any pair of theelectric wires 50, only the bulges 57 of one of the pair of the electricwires 50 will make point contact with the in-slot portions 51 of theother, thereby considerably reducing the frictional force applied to thein-slot portions 51. As a result, it is possible to prevent theinsulating coats 68 of the in-slot portions 51 of the electric wires 50from being damaged due to the frictional force. Moreover, after theelectric wires 50 are assembled together, each radially-adjacent pair ofthe in-slot portions 51 of the electric wires 50 will be kept apart fromeach other in the radial direction by the bulges 57 of the electricwires 50. Consequently, the creepage distances between the pinholesformed in the insulating coats 68 of the in-slot portions 51 of theelectric wires 50 will be increased. Accordingly, with the bulges 57, itis possible to reliably prevent insulation failure between the in-slotportions 51 of the electric wires 50.

In the present embodiment, in the electric wire forming step 101, eachof the electric wires 50 is also formed to include the bulges 58. Eachof the bulges 58 is formed on a radial end face of one of the bendsformed between the shoulder parts 55 and 56 of the turn portions 52 ofthe electric wire 50.

Consequently, after the electric wires 50 are assembled together, eachradially-adjacent pair of the turn portions 52 of the electric wires 50will be kept apart from each other in the radial direction by the bulges58 of the turn portions 52. As a result, the creepage distances betweenthe pinholes formed in the insulating coats 68 of the turn portions 52of the electric wires 50 will be increased. Accordingly, with the bulges58, it is possible to reliably prevent insulation failure between theturn portions 52 of the electric wires 50.

In the present embodiment, in the stator coil forming step 103, each ofthe operations of making relative axial movement between the rolledelectric wires 50 is performed by axially moving a first member toward asecond member; each of the first and second members is either one of therolled electric wires 50 or an electric wire assembly 50 b comprised ofplural of the rolled electric wires 50.

Consequently, it is possible to easily assemble all of the rolledelectric wires 50 together by sequentially performing the operations ofmaking relative axial movement between the rolled electric wires 50.

Further, in the present embodiment, in the stator coil forming step 103,each of the operations of making relative axial movement between therolled electric wires 50 is performed with at least one of the first andsecond members elastically deformed in a radial direction thereof.

Consequently, when the first member is axially moved toward the secondmember, interference between the first and second members can bereduced, thereby facilitating the assembly of the first and secondmembers and preventing the insulating coats 68 of the first and secondmembers from being damaged due to the interference.

In addition, the stator 20 according to the present embodiment ismanufactured by the above-described method. Accordingly, the stator 20has high dimensional accuracy, high insulation properties, and highreliability.

While the above particular embodiment of the present invention has beenshown and described, it will be understood by those skilled in the artthat various modifications, changes, and improvements may be madewithout departing from the spirit of the invention.

For example, FIG. 24A illustrates a first modification of the electricwires 50. In this modification, the half-turn portions 52M and 52N areformed to extend outward in the longitudinal direction of the electricwire 50 respectively from the first and twelfth in-slot portions 51A and51L. Consequently, the lead portions 53 a and 53 b are respectivelyoffset outward in the longitudinal direction from the first and twelfthin-slot portions 51A and 51L by the lengths of the half-turn portions52M and 52N.

FIG. 24B illustrates a second modification of the electric wires 50. Inthis modification, the half-turn portion 52M is formed to extend outwardin the longitudinal direction of the electric wire 50 from the firstin-slot portion 51A, whereas the half-turn portion 52N is formed toextend inward in the longitudinal direction from the twelfth in-slotportion 51L. Consequently, the lead portion 53 a is offset outward inthe longitudinal direction from the first in-slot portion 51A by thelength of the half-turn portion 52M, whereas the lead portion 53 b isoffset inward in the longitudinal direction from the twelfth in-slotportion 51L by the length of the half-turn portion 52N.

FIG. 25A illustrates a third modification of the electric wires 50. Inthis modification, the half-turn portion 52M is formed to extend inwardin the longitudinal direction of the electric wire 50 from the firstin-slot portion 51A, whereas the half-turn portion 52N is formed toextend outward in the longitudinal direction from the twelfth in-slotportion 51L. Consequently, the lead portion 53 a is offset inward in thelongitudinal direction from the first in-slot portion 51A by the lengthof the half-turn portion 52M, whereas the lead portion 53 b is offsetoutward in the longitudinal direction from the twelfth in-slot portion51L by the length of the half-turn portion 52N.

FIG. 25B illustrates a fourth modification of the electric wires 50. Inthis modification, both the half-turn portions 52M and 52N are omittedso that the lead portions 53 a and 53 b extend straight respectivelyfrom the first and twelfth in-slot portions 51A and 51L without beingoffset therefrom in the longitudinal direction of the electric wire 50.

FIG. 26 illustrates a fifth modification of the electric wires 50. Inthis modification, the shoulder parts 56 as shown in FIG. 12A areomitted from each of the turn portions 52 of the electric wires 50.Consequently, those parts between the crank-shaped part 54 and theshoulder parts 55 in each of the turn portions 52 of the electric wires50 become straight. As a result, the shape of the turn portions 52 ofthe electric wires 50 is simplified, thereby facilitating the shaping ofthe electric wires 50.

FIGS. 27A-27B illustrate a sixth modification of the electric wires 50.In this modification, both the half-turn portions 52M and 52N are shapedstraight without being stepped as shown in FIGS. 11A-11B. With thestraight shape of the half-turn portions 52M and 52N, the lead portions53 a and 53 b can be more easily and accurately positioned. In addition,it is also possible to shape only one of the half-turn portions 52M and52N straight.

In the previous embodiment, each of the turn portions 52 of the electricwires 50 includes the crank-shaped part 54 that is formed substantiallyat the center of the turn portion 52 for radially offsetting acorresponding pair of the in-slot portions 51 connected by the turnportion 52. However, the crank-shaped part 54 is not necessarily formedsubstantially at the center of the turn portion 52. For example, thecrank-shaped part 54 may be formed in the vicinity of one end of theturn portion 52.

In the previous embodiment, the amount of radial offset made by each ofthe crank-shaped parts 54 of the turn portions 52 is set to be equal tothe radial thickness of the in-slot portions 51 of the electric wires50. However, the amount of radial offset made by each of thecrank-shaped parts 54 may also be set to be, for example, 0.5, 1.5, or 2times the radial thickness of the in-slot portions 51. In such cases,the difference in radial distance from the axis O of the stator core 30between each adjacent pair of the in-slot portions 51, which areconnected by a corresponding one of the turn portions 52, would beaccordingly 0.5, 1.5, or 2 times the radial thickness of the in-slotportions 51.

In the previous embodiment, the corner portion 81 a of the first fixedjig 81 used in the electric wire forming step 101 is rounded with theconstant radius of curvature R to have a smooth curved outer surface.However, as shown in FIGS. 28A-28B, it is also possible to provide aprotrusion 81 b at the center of the curved outer surface of the cornerportion 81 a; the protrusion 81 b is rounded with a radius of curvaturesmaller than R. In this case, it is possible to facilitate the formationof the bulges 57 during the bending of the electric wire 50 against thefirst fixed jig 81. In addition, the protrusion 81 b may also beprovided on the curved outer surface of the corner portion 81 a so as tobe offset from the center of the curved outer surface.

In the previous embodiment, each of the bulges 57 is formed on a radialend face of one of the bends formed between the shoulder parts 55 of theturn portions 52 and the in-slot portions 51 of the electric wire 50. Inother words, each of the bulges 57 is formed on a radial end face of aportion of the electric wire 50 which falls on an imaginary lineextending straight from one of the in-slot portions 51 of the electricwire 50. However, it is also possible to form bulges on the radial endfaces of the in-slot portions 51 of the electric wire 50 using a pair offirst and second jigs 85 and 86 as shown in FIGS. 29A-29B.

More specifically, the first jig 85 is substantially U-shaped and has aplurality of (e.g., 4) protrusions 85 a that are formed on the innersurface of the bottom wall of the first jig 85. The second jig 86 isplate-shaped and has a plurality of (e.g., 4) through-holes 86 a. Informing the electric wire 50, the electric wire material 50 a is firstinterposed between the first and second jigs 85 and 86, with each of theprotrusions 85 a of the first jig 85 aligned with a corresponding one ofthe through-holes 86 a of the second jig 86. Then, the electric wirematerial 50 a is pressed between the first and second jigs 85 and 86.Consequently, portions of the electric wire material 50 a arerespectively extruded by the protrusions 85 a of the first jig 85 intothe through-holes 86 a of the second jig 86, thereby forming bulges 57 aon a radial end face (i.e., the upper face in FIGS. 29A-29B) of aportion of the electric wire material 50 a which makes up one of thein-slot portions 51 of the electric wire 50.

1. A method of manufacturing a stator for an electric rotating machine,wherein the stator comprises a hollow cylindrical stator core having aplurality of slots that are formed in a radially inner surface of thestator core and spaced in a circumferential direction of the statorcore, the method comprising the steps of: forming a plurality of planarelectric wires, each of the planar electric wires including a pluralityof in-slot portions to be received in the slots of the stator core and aplurality of turn portions to be located outside of the slots to connectthe in-slot portions; rolling each of the planar electric wires throughplastic deformation into a spiral or circular-arc shape; forming ahollow cylindrical stator coil by assembling the rolled electric wiresthrough operations of making relative axial movement therebetween; andassembling the stator core and the stator coil together to form thestator.
 2. The method as set forth in claim 1, wherein in the step offorming the planar electric wires, each of the planar electric wires isformed to include a plurality of first bulges, each of the first bulgesbeing formed, on a surface of one of the in-slot portions of the planarelectric wire or a surface of a portion of the planar electric wirewhich falls on an imaginary line extending straight from the in-slotportion, so as to protrude from the in-slot portion in a radialdirection of the stator core.
 3. The method as set forth in claim 2,wherein in the step of forming the planar electric wires, each of theplanar electric wires is formed so that each of the turn portions of theplanar electric wire includes a pair of shoulder parts, each of theshoulder parts adjoins one of the in-slot portions of the planarelectric wire and is bent at a substantially right angle to the in-slotportion to form a bend between the shoulder part and the in-slotportion, and each of the first bulges is formed on a surface of one ofthe bends formed between the shoulder parts of the turn portions and thein-slot portions of the planar electric wire.
 4. The method as set forthin claim 1, wherein in the step of forming the planar electric wires,each of the planar electric wires is formed so that each of the turnportions of the electric wires is stepped to include a plurality ofshoulder parts that extend substantially perpendicular to the in-slotportions, each of the planar electric wires is also formed to include aplurality of second bulges, and each of the second bulges is formed on asurface of one of bends formed between the shoulder parts of the turnportions of the planar electric wire so as to protrude in a radialdirection of the stator core.
 5. The method as set forth in claim 1,wherein in the step of forming the stator coil, each of the operationsof making relative axial movement is performed by axially moving a firstmember toward a second member, each of the first and second membersbeing one of the rolled electric wires or an electric wire assemblycomprised of a plurality of the rolled electric wires.
 6. The method asset forth in claim 5, wherein in the step of forming the stator coil,each of the operations is performed with at least one of the first andsecond members elastically deformed in a radial direction thereof.
 7. Astator for an electric rotating machine manufactured by the method asset forth in claim 1.